312 



THE VERTEBRATE SKELETON. 



median plate formed by the united neural arches. Laterally 

 they are continuous with the ischia. The first two of this 

 series of vertebrae are shown by their relation to the nerves 

 to be the true sacrals (fig. 58, B, 6), the remaining six belong- 

 ing to the caudal series. 



Behind them come the six free caudal vertebrae, succeeded 

 by a terminal piece, the pygostyle, formed of a number of 

 vertebrae fused together ; this bears the rectrices or tail quills. 



15 



18,. 



FIG. 59. SKULL OF A DUCK (Anas boschas). x 1. 

 A. Dorsal view of the cranium. B. Palatal view of the mandible. 



C. The Hyoid. 

 For numbers see Fig. 60. 

 B. THE SKULL. 



The skull of the duck, like that of birds in general, is 

 characterised (1) by its lightness, (2) by the contrast between 



